Canon vs Fuji: R5 Fail

Last summer, I thought to upgrade from the Fuji X-T4 to the Canon R5.

It didn’t last long.

I spent ages poring over specs sheets online, checking image quality, etc.

As a geek interested in various forms of nature photography (closeup, landscape and astrophotography), for over a decade I’ve made a habit of shooting more than one RAW per output image. Whether the scene in front of me benefits from simply average-stacking, HDR, focus-stacking, pixel-shift or panorama, the more data captured at source, the better an image can be produced and the more future-proof it is against further revisiting, potentially years down the line.

Given that I do a lot of my photography during weekend hikes around the countryside, in any given day I’m likely switching between these drive modes on a regular basis as I react to what’s in front of me.

This is where the Canon R5 falls down. For all that the specs suggest it might be a “perfect” camera for landscape, in reality it’s anything but. I found are three areas of major fault that nobody in any “review” seems to have noticed:

  1. The electronic shutter is arbitrarily limited to no longer than 0.5s shutter speed. This renders it impossible to make a focus-stack where the individual frames are any longer than that – so loch-shore landscapes are out. I contacted Canon Support about this and they said they had no plans to fix it.
  2. The 14-bit read-out is only available in burst modes slower than H+; in that mode it drops to 13-bit, potentially making images noisier.
  3. Switching between focus-stacking and exposure-bracketing is a massive pain in the backside. I had to use the My Menu to bring the two drive-modes closer; even so, switching between the two requires entering whichever is enabled, disabling it, going into the other, enabling it and checking the parameters. You can’t store either of these drive modes as an aspect of a custom user mode. If nothing else, it slows me down in the field.
  4. Canon’s attitude – corporate “Big Photo”(TM) – where the EF lens mount is well established, the RF mount is relatively immature and they used patents to stop third-party manufacturers producing RF lenses to protect their profits. Legally fine, but doesn’t sit well with me as playing nice.

I got a few good photos out of it, but the above loomed too large, destroyed my enthusiasm for it – big regret.

So I sold it after only a few months.

Fuji brought out the X-H2 while I wasn’t looking and it is far better suited to my taste.

  1. I know Fuji users tend to like the rangefinder-style exposure controls, but this has sensible PASM controls that allow storing actually useful combinations of settings in my 7 custom modes. (C1 = walk-around aperture-priority starting from f/5.6, auto ISO, colour, AEB; C2 = serious tripod-using landscape in manual mode, base ISO, 1s for long exposures, b&w preview, pixel-shift, …)
  2. 40MP is a major leap forward in APS-C sensors. It goes without saying that it’s 14-bit in any drive mode.
  3. In a first for Fuji, it supports pixel-shift
  4. The drive-modes are a button-push away – all of them including in-camera HDR, bracketing, focus-stacking and pixel-shift – and can be saved as part of a custom user mode.
  5. Long exposures are timed up to 15 minutes! No need for Bulb mode!
  6. The more I use the camera, the more I appreciate little things that show how well thought-out it is – memorably, where other cameras – Sony! – have a USB-C slot for power, transfer and remote control, the Fuji X-H2 has the USB-C slot for the first two but remote cable release is a micro-jack socket on the other side of the camera. So for astrophotography on a star-tracker, it’s an absolute beast – external powerbank coming in, shutter triggering automatically and pixel-shift as a form of dithering on 1-minute sub-exposures, it doesn’t get any better.

I don’t normally much care for brand allegiance – I’ll shift from Olympus to Pentax to Fuji to Sony to Fuji to Canon to Fuji if I think they suit me best at a given moment (over many years, I might add!) – but I can’t help notice this is now the third time I’ve come round to Fuji… it’s almost a habit.

Gear Change Time

Back in May I had a bit of a holiday. Figured the primary camera would be occupied taking timelapse video sequences for a couple of the evenings, and what happens if I find something else to take a photo of? So a friend suggested I get a Fuji X-T20.

Loved it.

Sold the K-1 dSLR and all the other Pentax kit, bought a Fuji X-H1 and some nice lenses to augment it.

Having spent all last Friday having the day off for the purposes of swapping the gear, I called in at Portknockie to make some photos of the well-known Bow Fiddle rock. The tide was low, requiring more care scrambling over the rocks.

Getting a bit more artistic, a long exposure view of the clouds passing by and a toned and tweaked edit:

The Zeiss 12mm f/2.8 Touit Fuji X-mount lens is a beauty. Being for APS-C crop-sensor only, it’s comparatively small, but elegantly formed with the curves flowing from lens-hood to body where the aperture and focus rings are smooth rubber perfectly integrated into the body.

I still maintain the most interesting views are to be found within the caves beside Bow Fiddle, not just staring at the lump itself. This is the first test image made with the Zeiss lens – sitting inside one of the caves, looking out, an HDR composite of 5 frames ±2/3EV each and even so it took a delicate touch getting the best RAW conversion and blend (haven’t used LuminanceHDR in ages!).

Testing my newly acquired Zeiss 12mm f/2.8 Touit lens – inside one of the caves looking out, of necessity a 5-shot HDR ±2/3EV. That lens is awesomely sharp, even with slightly elevated ISO around 640-1600.

Finally, one to relax with: the most serene simple composition of blue-grey sky with warm crepuscular rays spreading from behind a cloud. Light and sea, what more does one need?

Beautiful simplicity: a very cool blue-grey sky with orange crepuscular rays in the distance.

Knowing Your Lenses

Analysing Lens Performance

Background

Typically, when a manufacturer produces new lenses, they include an MTF chart to demonstrate the lens’s performance – sharpness measured as the number of line-pairs per millimetre it can resolve (to a given contrast tolerance), radially and sagitally, varying with distance from the centre of the image. While this might be useful before purchasing a lens, it does not make for easy comparisons (what if another manufacturer uses a different contrast tolerance?) nor does it necessarily well reflect the use to which it’ll be put in practice. (What if they quote a zoom’s performance at 28mm and 70mm f/5.6, but you shoot it most at 35mm f/8? Is the difference between radial and sagittal sharpness useful for a real-world scene?)
Further, if your lens has been around in the kit-bag a bit, is its performance still up to scratch or has it gone soft, with internal elements slightly out of alignment? When you’re out in the field, does it matter whether you use 50mm in the middle of a zoom or a fixed focal-length prime 50mm instead?
If you’re shooting landscape, would it be better to hand-hold at f/5.6 or stop-down to f/16 for depth of field, use a tripod and risk losing sharpness to diffraction?
Does that blob of dust on the front element really make a difference?
How bad is the vignetting when used wide-open?

Here’s a fairly quick experiment to measure and compare lenses’ performance by aperture, two ways. First, we design a test-chart. It’s most useful if the pattern is even across the frame, reflecting a mixture of scales of detail – thick and thin lines – at a variety of angles – at least perpendicular and maybe crazy pseudo-random designs. Here’s a couple of ideas:

Method

Decide which lenses, at which apertures, you want to profile. Make your own design, print it out at least A4 size, and affix it to a wall. We want the lighting to be as even as possible, so ideally use indoor artificial light after dark (ie this is a good project for a dark evening). Carefully, set up the camera on a tripod facing the chart square-on, and move close enough so the test-chart is just filling the frame.

Camera settings: use the lowest ISO setting possible (normally around 100), to minimize sensor noise. Use aperture-priority mode so it chooses the shutter-speed itself and fix the white-balance to counteract the indoor lighting. (For a daylight lightbulb, use daylight; otherwise, fluorescent or tungsten. Avoid auto-white-balance.)
Either use a remote-release cable or wireless trigger, or enable a 2-second self-timer mode to allow shaking to die down after pushing the shutter. Assuming the paper with the test-chart is still mostly white, use exposure-compensation (+2/3 EV).
For each lens and focal-length, start with the widest aperture and close-down by a third or half a stop, taking two photos at each aperture.
Open a small text-document and list each lens and focal-length in order as you go, along with any other salient features. (For example, with old manual prime lenses, note the start and final apertures and the interval size – may be half-stops, may be third of a stop.)
Use a RAW converter to process all the images identically: auto-exposure, fixed white-balance, and disable any sharpening, noise-reduction and rescaling you might ordinarily do. Output to 16-bit TIFF files.

Now, it is a given that a reasonable measure of pixel-level sharpness in an image, or part thereof, is its standard deviation. We can use the following Python script (requires numpy and OpenCV modules) to load image(s) and output the standard deviations of subsets of the images:

#!/usr/bin/env python

import sys, glob, cv, cv2
import numpy as np

def imageContrasts(fname):
  img = cv2.imread(fname, cv.CV_LOAD_IMAGE_GRAYSCALE)
  a=np.asarray(img)
  width=len(img[0])
  height=len(img[1])
  half=a[0:height//3, 0:width//3]
  corner=a[0:height//8, 0:width//8]
  return np.std(a), np.std(half), np.std(corner)

def main():
	files=sys.argv[1:]
	if len(files)==0:
		files=glob.glob("*.jpg")
	for f in files:
		co,cc,cf=imageContrasts(f)
		print "%s contrast %f %f %f" % (f, co, cc, cf)

if __name__=="__main__":
	main()

We can build a spreadsheet listing the files, their apertures and sharpnesses overall and in the corners, where vignetting typically occurs. We can easily make a CSV file by looping the above script and some exiftool magic across all the output TIFF files:

bash$ for f in *.tif
do
ap=$(exiftool $f |awk '/^Aperture/ {print $NF}' )
speed=$( exiftool $f |awk '/^Shutter Speed/ {print $NF}' )
conts=$(~/python/image-interpolation/image-sharpness-cv.py $f | sed 's/ /,/g')
echo $f,$ap,=$speed,$conts
done

Typical output might look like:

P1440770.tif,,=1/20,P1440770.tif,contrast,29.235214,29.918323,22.694936
P1440771.tif,,=1/20,P1440771.tif,contrast,29.253372,29.943765,22.739748
P1440772.tif,,=1/15,P1440772.tif,contrast,29.572350,30.566767,25.006098
P1440773.tif,,=1/15,P1440773.tif,contrast,29.513443,30.529055,24.942437

Note the extra `=’ signs; on opening this in LibreOffice Spreadsheet, the formulae will be evaluated and fractions converted to floating-point values in seconds instead. Remove the spurious `contrast’ column and add a header column (fname,aperture,speed,fname,overall,half,corner).

Analysis

Let’s draw some graphs. If you wish to stay with the spreadsheet, use a pivot table to average the half-image contrast values per aperture per lens and work off that. Alternatively, a bit of interactive R can lead to some very pretty graphs:

> install.package(ggplot2)
> library(ggplot2)
> data<-read.csv("sharpness.csv") 
> aggs<-aggregate(cbind(speed,entire,third,corner) ~lens+aperture, data, FUN=mean)
> qplot(aggs$aperture, aggs$third, col=aggs$lens, data=aggs, asp=.5)+geom_smooth()

This will give a comparison of overall sharpness by aperture, grouped by lens. Typically we expect every lens to have a sweetspot aperture at which it is sharpest; my own examples are no exception: third There are 5 lenses at play here: a kit 14-42mm zoom, measured at both 30mm and 42mm; a Minolta Rokkor 55mm prime; a Pentacon 30mm prime; and two Pentacon 50mm f/1.8 prime lenses, one brand new off eBay and one that’s been in the bag for 4 years.

The old Pentacon 50mm was sharpest at f/5.6 but is now the second-lowest at almost every aperture – we’ll come back to this. The new Pentacon 50mm is sharpest of all the lenses from f/5 onwards, peaking at around f/7.1. The kit zoom lens is obviously designed to be used around f/8; the Pentacon 30mm prime is ludicrously unsharp at all apertures – given a choice of kit zoom at 30mm or prime, it would have to be the unconventional choice every time. And the odd one out, the Rokkor 55mm, peaks at a mere f/4.

How about the drop-off, the factor by which the extreme corners are less sharp than the overall image? Again, a quick calculation and plot in R shows:

> aggs$dropoff < - aggs$corner / aggs$third
> qplot(aggs$aperture, aggs$dropoff, col=aggs$lens, data=aggs, asp=.5)+geom_smooth()

dropoff Some observations:

  • all the lenses show a similar pattern, worst vignetting at widest apertures, peaking somewhere in the middle and then attenuating slightly;
  • there is a drastic difference between the kit zoom lens at 30mm (among the best performances) and 42mm (the worst, by far);
  • the old Pentacon 50mm lens had best drop-off around f/8;
  • the new Pentacon 50mm has least drop-of at around f/11;
  • the Minolta Rokkor 55mm peaks at f/4 again.

So, why do the old and new Pentacon 50mm lenses differ so badly? Let’s conclude by examining the shutter-speeds; by allowing the camera to automate the exposure in aperture-priority mode, whilst keeping the scene and its illumination constant, we can plot a graph showing each lens’s transmission against aperture.

> qplot(aggs$aperture, log2(aggs$speed/min(aggs$speed)), col=aggs$lens, data=aggs, asp=.5)+geom_smooth()

speed Here we see the new Pentacon 50mm lens seems to require the least increase in shutter-speed per stop aperture, while, above around f/7.1, the old Pentacon 50mm lens requires the greatest – rocketing off at a different gradient to everything else, such that by f/11 it’s fully 2 stops slower than its replacements.

There’s a reason for this: sadly, the anti-reflective coating is starting to come off in the centre of the front element of the old lens, in the form of a rough circle approximately 5mm diameter. At around f/10, the shutter iris itself is 5mm, so this artifact becomes a significant contributor to the overall exposure.

Conclusion

With the above data, informed choices can be made as to which lens and aperture suit particular scenes. When shooting a wide-angle landscape, I can use the kit zoom at f/8; for nature and woodland closeup work where the close-focussing distance allows, the Minolta Rokkor 55mm at f/4 is ideal.